Along with the development of automobile technologies and people's high requirement on aesthetic quality of vehicles, the vehicle appearance is demanded to be made increasingly finer and vehicle manufacturers spend more efforts devoted to optimization of details. When a vehicle breaks down, it is usually hauled by a trailer. At this moment, a metal tow hook of the trailer passes through a hole located on the bumper so as to connect the vehicle body. When there is no need to be connected with the trailer, the hole on the bumper is covered by a tow hook cover plate. Therefore, the tow hook cover plate, usually mounted on the bumper, is an important member of appearance and the aesthetical quality of the coordination with its surrounding parts draws more and more attention of manufacturers and customers. It's a similar case for another type of cover plate used on any other vehicle outer body part. At the same time, the vehicle appearance presents more and more diversity, and the conventional cover plate is rotary. It's difficult to set a proper rotational shaft for the rotary cover plate in certain positions due to its surface shape, since the cover plate will collide with the surrounding parts in its turning (rotation) process. This will in turn cause product abrasions and affect the appearance.